Extrusion & Post
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Uneven thickness of low density polyethylene blown film
Problem Phenomenon
Film thickness fluctuates greatly in the circumferential or longitudinal direction, with thickness deviation exceeding ±10%.
Uneven thickness affects film mechanical and use performance, and may cause wandering or film breakage on automatic packaging machines.
Cause Analysis
(1) Uneven die gap
(2) Uneven temperature around the die circumference
(3) Uneven air ring cooling
(4) Extrusion output fluctuation
(5) Unstable haul-off speed
Solution
(1) Adjust die gap, circumferential error not exceeding ±0.01mm
(2) Check die heater bands, ensure circumferential temperature difference not exceeding ±3°C (160-220°C range)
(3) Check the air ring, ensure uniform air output, regularly clean the air ring
(4) Stabilize extruder screw rotation speed and temperature
(5) Stabilize haul-off speed, use high-precision haul-off control system
Key Takeaway
Uneven film thickness is caused by uneven die gap, temperature, or cooling; it needs to be solved from mold accuracy and process stability.
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